fix: install python3-venv and python3-pip for non-root venv creation

Users hit a dependency loop: python3-venv missing → can't create venv →
can't install packages → no root to apt install at runtime.
Installing at build time unblocks standard python3 -m venv usage.
uv venv also works as an alternative (uv is in PATH via profile.d).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -10,6 +10,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     curl \
     jq \
     python3 \
+    python3-venv \
+    python3-pip \
     chromium \
     libnss3 \
     libatk1.0-0 \